Terminally modified acrylic polymer and method for producing terminallly modified acrylic polymer

ABSTRACT

The present invention provides a terminally modified acrylic polymer having excellent thermal decomposition properties at low temperatures, an inorganic fine particle dispersed paste composition obtained by using the terminally modified acrylic polymer and a method of producing of the terminally modified acrylic polymer. 
     The present invention pertains to a terminally modified acrylic polymer, which comprises a main chain composed of a repeating unit represented by the following formula (1), and a group represented by the following formula (2) at both ends or one end of the main chain, 
     
       
         
         
             
             
         
       
         
         
           
             wherein R 1  represents hydrogen atom, an organic group having 1 or more carbon atoms or a derivative of an organic group having 1 or more carbon atoms; R 2  represents an organic group having 1 or more carbon atoms or a derivative of an organic group having 1 or more carbon atoms; R 3  and R 4  each represents hydrogen atom, an organic group having 1 or more carbon atoms or a derivative of an organic group having 1 or more carbon atoms; and n represents a positive integer.

TECHNICAL FIELD

The present invention relates to a terminally modified acrylic polymerhaving excellent thermal decomposition properties at low temperatures,an inorganic fine particle dispersed paste composition obtained by usingthe terminally modified acrylic polymer and a method of producing of theterminally modified acrylic polymer.

BACKGROUND ART

In recent years, paste compositions formed by dispersing inorganic fineparticles such as conductive powder, ceramic powder and the like in abinder resin are employed in order to obtain sintered bodies havingvarious shapes. Particularly, a paste composition formed by dispersing aphosphor as fine particles in a resin binder is used, for example, inplasma displays (PDP), field emission displays (FED, SED), and the like,and in recent years, its demand is being increased. Also in the case ofa paste composition formed by dispersing glass frits in a resin binder,a resin for a lead-free frit glass, which does not impair conventionalhandling and has a lower decomposition temperature than that of a resinfor a conventional lead frit glass, is being required. Moreover, demandsfor uses of conductive paste for wiring, which uses a silver powderhaving a low sintering temperature, is growingly increased.

As the binder resin used for such an inorganic fine particle dispersedpaste composition, a cellulose type resin such as ethyl cellulose fromwhich a paste excellent in a screen printing property can be obtained iscommonly employed. However, when considering a process in whichinorganic fine particles are dispersed, a pattern is printed by screenprinting, and degreasing and burning are performed to obtain aninorganic fine particle layer, since cellulose type resins have poorthermal decomposition properties, they have to be degreased at elevatedtemperatures and therefore they have problems that large energy isrequired in a production step or it takes much time to burn.Furthermore, when a cellulose type resin is used as a binder resin of apaste in which glass frits are dispersed, there is a problem that acarbon derived from a resin remains in a sintered body since in the stepof sintering glass frits, sintering of the glass frit starts before theresin is decomposed and removed.

For this problem, in Patent Document 1, a paste composition obtained byusing an acrylic resin having excellent thermal decomposition propertiesis disclosed. An inorganic fine particle dispersed paste compositioncontaining such an acrylic resin can be burnt at low temperatures in ashort time since its binder resin has good thermal decompositionproperties.

However, even in such a case, when low melting point glasses having asoftening point of 400° C. or lower or inorganic fine particles such asconductive fine particles of copper or silver, which are prone to beingoxidized by sintering, are used, decomposition at lower temperatures isrequired.

Patent Document 1: Japanese Kokai Publication Hei-11-71132 (JP-AH11-71132)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In view of the above description, it is an object of the presentinvention to provide a terminally modified acrylic polymer havingexcellent thermal decomposition properties at low temperatures, aninorganic fine particle dispersed paste composition obtained by usingthe terminally modified acrylic polymer and a method of producing of theterminally modified acrylic polymer.

Means for Solving the Problems

The present invention is a terminally modified acrylic polymer, whichcontains a main chain composed of a repeating unit represented by thefollowing formula (1), and a group represented by the following formula(2) at both ends or one end of the main chain.

In the above formulas, R¹ represents hydrogen atom, an organic grouphaving 1 or more carbon atoms or a derivative of an organic group having1 or more carbon atoms; R² represents an organic group having 1 or morecarbon atoms or a derivative of an organic group having 1 or more carbonatoms; R³ and R⁴ each represents hydrogen atom, an organic group having1 or more carbon atoms or a derivative of an organic group having 1 ormore carbon atoms; and n represents a positive integer.

Hereinafter, the present invention will be described in detail.

The terminally modified acrylic polymer of the present invention has amain chain comprising repeating units represented by the above formula(1).

R¹ in the formula (1) is hydrogen atom, an organic group having 1 ormore carbon atoms or a derivative of an organic group having 1 or morecarbon atoms.

Examples of the organic group having 1 or more carbon atoms or thederivative of an organic group having 1 or more carbon atoms, used inthe R¹, include straight chain, branched chain or cyclic alkyl groupshaving 1 to 8 carbon atoms, such as methyl group, ethyl group, n-propylgroup, isopropyl group, cyclopropyl group, n-butyl group, sec-butylgroup, tert-butyl group, cyclobutyl group, n-pentyl group, n-hexylgroup, n-heptyl group, n-octyl group, and the like, and derivativesthereof. Among these groups, straight chain or branched chain alkylgroups having 1 to 4 carbon atoms are preferred, and methyl group orethyl group are more preferred.

Among these, it is preferred that the R¹ is methyl group and the formula(1) is a segment derived from a methacrylic ester.

R² in the formula (1) is an organic group having 1 or more carbon atomsor a derivative of an organic group having 1 or more carbon atoms. Whenthe organic group has 0 carbon atom, since the terminally modifiedacrylic polymer is (meth)acrylic acid polymer which is a polycarboxylicacid, there is a problem that it is difficult to dissolve the terminallymodified acrylic polymer or a solvent in which the terminally modifiedacrylic polymer is dissolved is limited.

Examples of the organic group having 1 or more carbon atoms or thederivative of the organic group having 1 or more carbon atoms, used inthe R², include methyl group, ethyl group, n-propyl group, isopropylgroup, cyclopropyl group, n-butyl group, sec-butyl group, tert-butylgroup, isobutyl group, cyclobutyl group, n-pentyl group, n-hexyl group,cyclohexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group,n-nonyl group, n-dodecyl group, behenyl group, stearyl group,isomyristyl group, isoboronyl group, phenyl group, benzyl group,2-hydroxyethyl group, 2-hydroxypropyl group, 2,3-dihydropropyl group,4-hydroxybutyl group, 4-hydroxymethyl group, phenyl group,4-methylphenyl group, 3-methylphenyl group, 2-methylphenyl group,4-hydroxyphenyl group, 4-acetoxyphenyl group, 4-tert-butoxyphenyl group,and the like, and derivatives thereof.

As an alkyl group having 1 or more carbon atoms or a derivative of analkyl group having 1 or more carbon atoms, used in the R², the same oneas in the R¹ may be used. In addition, R¹ and R² may be the same or maybe different from each other.

When the terminally modified acrylic polymer of the present invention isused for an inorganic fine particle dispersed paste composition, aterminally modified acrylic polymer in which R² is an alkyl group having1 to 8 carbon atoms is preferably used. Thereby, thermal decompositionderived from a main chain structure of a resin can be expected, and aninorganic fine particle dispersed paste composition having an excellentdecomposition property of a binder can be prepared. When the alkyl grouphas more than 8 carbon atoms, decomposition properties of the binder maybe deteriorated due to the thermal decomposition properties of a sidechain alkyl group.

The terminally modified acrylic polymer of the present invention has agroup represented by the above formula (2) at both ends or one end ofthe main chain. By having the group represented by the formula (2) atboth ends or one end, since thermal decomposition starts from an end ofthe molecule of the terminally modified acrylic polymer of the presentinvention in heating the terminally modified acrylic polymer, theterminally modified acrylic polymer of the present invention can be aresin which is promptly decomposed at low temperatures and is extremelysuperior in a thermal decomposition property.

R³ and R⁴ in the formula (2) are hydrogen atom, an organic group having1 or more carbon atoms or a derivative of an organic group having 1 ormore carbon atoms.

Examples of the R³ and R⁴ include hydrogen atom, methyl group, ethylgroup, n-propyl group, isopropyl group, cyclopropyl group, n-butylgroup, sec-butyl group, tert-butyl group, isobutyl group, cyclobutylgroup, n-pentyl group, n-hexyl group, cyclohexyl group, n-heptyl group,n-octyl group, 2-ethylhexyl group, n-nonyl group, n-dodecyl group,behenyl group, stearyl group, isomyristyl group, isoboronyl group,phenyl group, benzyl group, 2-hydroxyethyl group, 2-hydroxypropyl group,2,3-dihydropropyl group, 4-hydroxybutyl group, 4-hydroxymethyl group,phenyl group, 4-methylphenyl group, 3-methylphenyl group, 2-methylphenylgroup, 4-hydroxyphenyl group, 4-acetoxyphenyl group, and4-tert-butoxyphenyl group. Substituents such as hydrogen atom, methylgroup, ethyl group, n-propyl group, isopropyl group and cyclopropylgroup can be suitably used from the viewpoint of ease of terminalmodification. Among these, hydrogen atom is particularly preferable.

As the R³ and the R⁴, the same functional group may be used or differentfunctional groups may be used.

A preferred lower limit of the number average molecular weight on thepolystyrene equivalent basis of the terminally modified acrylic polymerof the present invention is 2000 and a preferred upper limit is 1000000.When the above number average molecular weight is less than 2000,sufficient viscosity may not be attained for example when the terminallymodified acrylic polymer of the present invention is used as a binderresin of a paste composition. When the number average molecular weightis more than 1000000, an adhesive force may be too strong or theapplication of the acrylic polymer may be difficult due to significantincrease in viscosity for example when the terminally modified acrylicpolymer of the present invention is used as a binder resin of a pastecomposition. A more preferred upper limit of the number averagemolecular weight is 500000.

In addition, in the present specification, the number average molecularweight is a value found on the polymethyl methacrylate equivalent basismeasured by gel permeation chromatography (GPC).

When the terminally modified acrylic polymer of the present invention isused for an inorganic fine particle dispersed paste composition, thenumber average molecular weight of the acrylic polymer is preferably2000 to 500000. Thereby, it becomes easy to prepare an inorganic fineparticle dispersed paste composition which is superior in handling. Whenthe number average molecular weight is less than 2000, the viscosity ofthe prepared paste is significantly low, and therefore, the dispersionstability of the inorganic fine particle may be impaired. When thenumber average molecular weight is more than 500000, the viscosity of aninorganic fine particle dispersed paste composition to be obtained maybe significantly high, and the application of the paste composition to aprocess such as printing or coating may be difficult.

A preferred upper limit of a molecular weight distribution (PDI=Mw/Mn)of the terminally modified acrylic polymer of the present invention is2.0. When the molecular weight distribution is more than 2.0, theacrylic polymer may tend to be stringy and may be hard to handle whenthe acrylic polymer is used in a paste.

Examples of a method of producing the terminally modified acrylicpolymer of the present invention include a method comprising a step ofreacting a living radical polymerization initiator represented by thefollowing formula (3-1) or (3-2) with an acrylic monomer represented bythe following formula (4) to prepare an acrylic polymer and a step ofreacting the acrylic polymer with a nitroxyl radical represented by thefollowing formula (5) or (6) to modify both ends or one end of theacrylic polymer through olefination by hydrogen abstraction from analkyl group of a position, and a method comprising a step of reactingthe acrylic polymer with diselenide such as diphenyl diselenide insteadof nitroxyl radical to obtain a polymer with terminal selenium andreacting the obtained polymer with an oxidizing agent such as hydrogenperoxide.

Among these methods, the method comprising a step of reacting a livingradical polymerization initiator represented by the following formula(3-1) or (3-2) with an acrylic monomer represented by the followingformula (4) to prepare an acrylic polymer, and a step of reacting theacrylic polymer with a nitroxyl radical represented by the followingformula (5) or (6) to modify both ends or one end of the acrylic polymeris preferable. Such a method of producing a terminally modified acrylicpolymer also constitutes the present invention.

In the above formulas, R⁵ to R¹² represent hydrogen atom, an organicgroup having 1 or more carbon atoms or a derivative of an organic grouphaving 1 or more carbon atoms, R¹³ represents a derivative of a divalentorganic group having 3 or more carbon atoms, and X represents Bi, Te, Sbor iodine. In addition, when X is iodine, X is not replaced with R⁶.

Examples of the organic group having 1 or more carbon atoms or thederivative of the organic group having 1 or more carbon atoms, used inthe R⁵ to R¹², include a methyl group, ethyl group, n-propyl group,isopropyl group, cyclopropyl group, n-butyl group, sec-butyl group,tert-butyl group, isobutyl group, cyclobutyl group, n-pentyl group,n-hexyl group, cyclohexyl group, n-heptyl group, n-octyl group,2-ethylhexyl group, n-nonyl group, n-dodecyl group, behenyl group,stearyl group, isomyristyl group, isoboronyl group, phenyl group, benzylgroup, 2-hydroxyethyl group, 2-hydroxypropyl group, 2,3-dihydropropylgroup, 4-hydroxybutyl group, 4-hydroxymethyl group, phenyl group,4-methylphenyl group, 3-methylphenyl group, 2-methylphenyl group,4-hydroxyphenyl group, 4-acetoxyphenyl group, 4-tert-butoxyphenyl group.As the R⁵ to R¹², different functional groups may be used or the samefunctional group may be used in combination.

In the step of reacting a living radical polymerization initiatorrepresented by the above formula (3-1) or (3-2) with an acrylic monomerrepresented by the formula (4) to prepare an acrylic polymer, forexample, the living radical polymerization initiator represented by theformula (3-1) or (3-2) is mixed with the acrylic monomer represented bythe formula (4) in a container, the inside of which is replaced with aninert gas. Examples of the inert gas include nitrogen, argon, helium,and the like. Among these gases, argon and nitrogen are preferred.

Incidentally, this step is described in detail in Japanese Journal ofPolymer Science and Technology (Kobunshi Ronbun shu), vol. 64, p 329,2007 and its cited references.

The proportion between the living radical polymerization initiatorrepresented by the above formula (3-1) or (3-2) and the acrylic monomerrepresented by the formula (4) may be appropriately adjusted dependingon a molecular weight or a molecular weight distribution of an acrylicpolymer to be obtained, but it is preferred to add 20 to 100000 mol ofthe acrylic monomer represented by the formula (4) to 1 mol of theliving radical polymerization initiator represented by the formula (3-1)or (3-2).

Preparation of the acrylic polymer is generally performed without usinga solvent, but an organic solvent which is commonly used in radicalpolymerization may be used. Examples of the organic solvent includebenzene, toluene, xylene, anisole, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetone, methyl ethyl ketone, methyl isobutyl ketone,tetrahydrofuran (THF), ethyl acetate, butyl acetate,trifluoromethylbenzene, butyl carbitol, butyl carbitol acetate,terpineol, dihydroterpineol, texanol, pentane, hexane, cyclohexane,methylcyclohexane, cyclohexanone, and dioctyl phthalate. Further, anaqueous solvent can also be used, and examples of the aqueous solventinclude water, methanol, ethanol, isopropanol, n-butanol, ethylcellosolve, butyl cellosolve, and 1-methoxy-2-propanol.

Next, in the step of preparing the acrylic polymer, a mixture comprisingthe living radical polymerization. initiator represented by the formula(3-1) or (3-2) and the acrylic monomer represented by the formula (4) isstirred. A reaction temperature and a reaction time may be appropriatelyadjusted depending on a molecular weight or a molecular weightdistribution of an acrylic polymer to be obtained, but it is preferredthat the mixture is generally stirred at a temperature of 60 to 150° C.for 5 to 100 hours, and it is preferred that the mixture is stirred at atemperature of 80 to 120° C. for 10 to 30 hours. In this case, apressure at the time of reaction is usually a normal pressure, butpressurized condition or a reduced pressure may be employed.

After the completion of the reaction, a resin is isolated by removingthe used solvent and the residual monomer under a reduced pressure by anormal method, and by taking out the resulting resin or using a solventin which the resin is not dissolved to perform reprecipitation.

In the method of producing a terminally modified acrylic polymer of thepresent invention, plural kinds of acrylic monomers may be used. Forexample, when two or more kinds of acrylic monomers are simultaneouslyreacted with each other, a random copolymer can be obtained. Further, byreacting different kinds of acrylic monomers sequentially, a blockcopolymer can be obtained.

Examples of the the living radical polymerization initiator representedby the formula (3-1) or (3-2) include methyl2-methyl-2-dimethylbismuthanyl propionate,2-methyl-2-diphenylbismuthanyl propionitrile,2-methyl-2-dimethylphenylbismuthanyl propionitrile, methyl2-methyl-2-dimethylstibanyl propionate, 2-methyl-2-dimethylstibanylpropionitrile, 1-dimethylstibanyl-1-phenyl ethane, ethyl2-methyl-2-methyltellanyl propionate, ethyl 2-n-butyl-2-phenyltellanylpropionate, ethyl 2-methyl-2-phenyltellanyl propionate,2-methyl-2-methyltellanyl propionitrile, 1-methyltellanyl-1-phenylethane, and 1-phenyltellanyl-1-phenyl ethane.

Examples of the acrylic monomer represented by the above formula (4)include methyl(meth)acrylate, ethyl(meth)acrylate,n-propyl(meth)acrylate, isopropyl(meth)acrylate, cyclopropyl(meth)acrylate, n-butyl(meth)acrylate, sec-butyl(meth)acrylate,tert-butyl(meth)acrylate, isobutyl(meth)acrylate,cyclobutyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate,cyclohexyl(meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate,2-ethylhexyl(meth)acrylate, n-nonyl(meth)acrylate,n-dodecyl(meth)acrylate, behenyl(meth)acrylate, stearyl(meth)acrylate,isomyristyl(meth)acrylate, isoboronyl(meth)acrylate,phenyl(meth)acrylate, benzyl(meth)acrylate,2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,2,3-dihydropropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate,4-hydroxymethyl(meth)acrylate, phenyl(meth)acrylate,4-methylphenyl(meth)acrylate, 3-methylphenyl(meth)acrylate,2-methylphenyl(meth)acrylate, 4-hydroxyphenyl(meth)acrylate,4-acetoxyphenyl(meth)acrylate, and 4-tert-butoxyphenyl(meth)acrylate,polymethyl methacrylate with terminal(meth)acryloyl, polyethylene glycolmono(meth)acrylic ester, polypropylene glycol mono(meth)acrylic ester,polytetramethylene glycol mono(meth)acrylic ester, andpolydimethylsiloxane mono(meth)acrylic ester. Among these, alkylmethacrylate, particularly, methyl methacrylate, ethyl methacrylate,isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexylmethacrylate, and lauryl methacrylate are preferred. Further, randomcopolymerization, block copolymerization, multi-block copolymerization,or alternative copolymerization may be performed by use of these pluralkinds of acrylic monomers. When performing these copolymerizationprocesses, it is preferable to select an acrylic monomer havingexcellent thermal decomposition properties.

Furthermore, a vinyl monomer may be copolymerized for the purpose ofimparting other properties. Examples of the vinyl monomer includestyrene, α-methyl styrene, p-methyl styrene, maleic anhydride,maleimide, (meth)acrylamide, N-(meth)acryloylmorpholine,(meth)acrylonitrile, and N-isopropyl(meth)acrylamide.

In the method of producing an terminally modified acrylic polymer of thepresent invention, next, the step of reacting the obtained acrylicpolymer with a nitroxyl radical represented by the above formula (5) or(6) to modify both ends or one end of the above acrylic polymer througholefination by hydrogen abstraction from an alkyl group of a position isperformed.

In the step of modifying the end, a method of modifying both ends or oneend of the acrylic polymer is not particularly limited and publiclyknown methods can be employed. For example, a method, in which apredetermined amount of the acrylic polymer and the nitroxyl radicalrepresented by the formula (5) or (6) are put in an organic solvent suchas benzene to react them, are employed.

Examples of the nitroxyl radical represented by the above formula (5) or(6) include N,N-di-tert-butylamine-N-oxy,N-amyl-N-tert-butylamine-N-oxy,N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)]-amine-N-oxy,N-tert-butyl-N-(1-phenyl-2-methyl)propylamine-N-oxy,N-tert-butyl-N-(1-tert-butyl-2-ethylsulfinyl)propylamine-N-oxy,2,2,6,6-tetramethylpiperidine-1-oxy,2,2,6,6-tetraethyl-4-oxo-piperidine-1-oxy,2,6-bis(tert-butyldimethyl)siloxy-2,6-diethylpiperidine-1-oxy, and2,2,10,10-tetraethylisoindoline-N-oxy. These nitroxyl radicals may beused alone or in combination of two or more kinds.

An amount of the nitroxyl radical represented by the above formula (5)or (6) to be added may be appropriately adjusted depending on propertiesof the terminally modified acrylic polymer to be obtained, but it ispreferred to add 0.8 to 3.0 mol of the nitroxyl radical represented bythe formula (5) or (6) to 1 mol of the acrylic polymer.

An inorganic fine particle dispersed paste composition containing theterminally modified acrylic polymer of the present invention, an organicsolvent, and an inorganic fine particle also constituted the presentinvention.

The organic solvent is not particularly limited and examples thereofinclude ethylene glycol ethyl ether, ethylene glycol monobutyl ether,ethylene glycol monoethyl ether acetate, butyl carbitol, butyl carbitolacetate, isophorone, butyl formate, butyl lactate, butyl acetate,isobutyl acetate, tert-butyl acetate, propyl acetate, isopropyl acetate,ethyl acetate, dioctyl phthalate, dibutyl phthalate, dioctyl adipate,dibutyl adipate, benzyl alcohol, phenyl propylene glycol, terpineol,terpinolene, dihydroterpineol, α-pinene, β-pinene, limonene, toluene,xylene, mesitylene, cresol, acetone, methyl ethyl ketone, methylisobutyl ketone, cyclohexanone, 2,4-pentanedione, methanol, ethanol,isopropyl alcohol, 1-propanol, 1-butanol, 2-butanol, isobutyl alcohol,tert-butyl alcohol, cyclohexanol, amyl alcohol, 2-ethylhexyl alcohol,1-octyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, dipropylene glycol, tripropylene glycol,1,4-butanediol, glycerin, hexane, cyclohexane, methylcyclohexane,heptane, octane, isooctane, 2-ethylhexane, nonane, decane, and decalin.

Among these, butyl carbitol, butyl carbitol acetate, and terpineol aresuitably used since they are superior in the solubility of binder resincomprising a (meth)acrylic resin therein and in the viscosity control.These organic solvents may be used alone or in combination of two ormore kinds.

As the above organic solvent, a solvent, in which a boiling point at 1atm is lower than 400° C., is preferably employed so that the pastecomposition can be burnt at low temperatures, more preferably, a boilingpoint at 1 atm is lower than 350° C., and furthermore preferably, aboiling point at 1 atm is lower than 300° C. Moreover, a solvent inwhich a boiling point at 1 atm is at least 100° C. or higher ispreferable in order to inhibit changes in a solid content or changes inviscosity due to solvent volatilization during use and storage of thepaste. The boiling point at 1 atm is more preferably 150° C. or higher.It is particularly preferred that the boiling point at 1 atm is 100 to290° C. When the boiling point is lower than 100° C., disadvantages thata solvent is volatilized during storage of the paste composition andtherefore viscosity is not stable or the surface causes drying mayoccur. When the boiling point is higher than 290° C., there is a problemthat it is difficult to adequately dry an applied substance in a dryersuch as an oven, or a problem that an applied substance is thermallydegraded if a drying temperature is increased in order to adequately drythe applied substance.

Examples of the inorganic fine particle include metal powders such as agold powder, a silver powder, a copper powder, a nickel powder, aplatinum powder, a palladium powder, and the like; powders of metaloxides such as silica, alumina, zirconia, titania, zinc oxide, magnesia,ferrite, ITO, and the like; frits of glasses such as soda glass,alkali-free glass, lead borosilicate glass, bismuth borosilicate, zincborosilicate glass, and the like; powders of nitrides such as aluminumnitride, silicon nitride, boron nitride, and the like; a phosphorpowder, a silicon carbide powder, a barium titanate powder, and a carbonpowder. Among these fine particles, a glass frit, a phosphor powder, asilver powder, a copper powder, an ITO powder, a zinc oxide powder and acarbon powder are preferable.

Effect of the Invention

In accordance with the present invention, it is possible to provide aterminally modified acrylic polymer having excellent thermaldecomposition properties at low temperatures, an inorganic fine particledispersed paste composition obtained by using the terminally modifiedacrylic polymer and a method of producing of the terminally modifiedacrylic polymer.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail byway of examples, but the present invention is not limited to theseexamples.

EXAMPLE 1 (Production of Acrylic Polymer)

30 mol of methyl methacrylate (manufactured by Wako Pure ChemicalIndustries, Ltd.) as a monomer was added to 1 mol of an organic bismuthcompound CH₃C(CH₃)(Bi(CH₃)₂)COOCH₃ as a living radical polymerizationinitiator, and then, the resulting mixture was heated to 100° C. whilestirring the mixture with a stirrer and maintained at this temperaturefor 3 hours. After the completion of a reaction, the reaction solutionwas dissolved in 15 mL of α,α,α-trifluorotoluene. To the resultingsolution, 0.2 g of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPOmanufactured by Aldrich Chemical Co.) was further added and theresulting mixture was reacted at 80° C. for 1 hour. After the completionof a reaction, the resulting solution was charged into 250 mL of hexane(manufactured by Wako Pure Chemical Industries, Ltd.) being stirred.Thereafter, a precipitated polymer was filtered under suction and driedto obtain a terminally modified acrylic polymer (conversion rate 97%).

The obtained terminally modified acrylic polymer was analyzed by gelpermeation chromatography (GPC) using LF-804 Column manufactured bySHOKO Co., Ltd. as a column to determine a number average molecularweight on the polymethyl methacrylate equivalent basis and a molecularweight distribution (PDI=Mw/Mn). The results are shown in Table 1.

Further, an NMR spectrum of the obtained terminally modified acrylicpolymer is shown in FIG. 2. From the NMR spectrum shown in FIG. 2, it isfound that a polymer having a terminal olefin is prepared.

In addition, the organic bismuth compound as a living radicalpolymerization initiator was prepared based on the reference (S. Yamago,E. Kayahara, M. Kotani, B. Ray, Y. Kwak, A. Goto and T. Fukuda, Angew.Chem. Int. Ed., 46, p 1304-1306 (2007)).

EXAMPLE 2 (Production of Acrylic Polymer)

30 mol of isobutyl methacrylate (manufactured by Wako Pure ChemicalIndustries, Ltd.) as a monomer was added to 1 mol of an organic bismuthcompound CH₃C(CH₃)(Bi(CH₃)₂)COOCH₃ as a living radical polymerizationinitiator, and then, the resulting mixture was heated to 100° C. whilestirring the mixture with a stirrer and maintained at this temperaturefor 3 hours. After the completion of a reaction, the reaction solutionwas dissolved in 15 mL of α,α,α-trifluorotoluene. To the resultingsolution, 0.2 g of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPOmanufactured by Aldrich Chemical Co.) was further added and theresulting mixture was reacted at 80° C. for 1 hour. After the completionof a reaction, the resulting solution was charged into 250 mL of hexane(manufactured by Wako Pure Chemical Industries, Ltd.) being stirred.Thereafter, a precipitated polymer was filtered under suction and driedto obtain a terminally modified acrylic polymer (conversion rate 95%).

Further, the obtained terminally modified acrylic polymer was measuredby NMR, and consequently, it could be verified that the acrylic polymerhad a functional group represented by the formula (2) at the end.

The obtained terminally modified acrylic polymer was analyzed by gelpermeation chromatography (GPC) using LF-804 Column manufactured bySHOKO Co., Ltd. as a column to determine a number average molecularweight on the polymethyl methacrylate equivalent basis and a molecularweight distribution (PDI=Mw/Mn). The results are shown in Table 1.

EXAMPLE 3 (Production of Acrylic Polymer)

A mixture solution of 15 mol of isobutyl methacrylate (manufactured byWako Pure Chemical Industries, Ltd.) and 15 mol of isobutyl methacrylate(manufactured by Wako Pure Chemical Industries, Ltd.) as a monomer wasadded to 1 mol of an organic bismuth compound CH₃C(CH₃)(Bi(CH₃)₂)COOCH₃as a living radical polymerization initiator, and then, the resultingmixture was heated to 100° C. while stirring the mixture with a stirrerand maintained at this temperature for 3 hours. After the completion ofa reaction, the reaction solution was dissolved in 15 mL ofα,α,α-trifluorotoluene. To the resulting solution, 0.2 g of2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO manufactured by AldrichChemical Co.) was further added and the resulting mixture was reacted at80° C. for 1 hour. After the completion of a reaction, the resultingsolution was charged into 250 mL of hexane (manufactured by Wako PureChemical Industries, Ltd.) being stirred. Thereafter, a precipitatedpolymer was filtered under suction and dried to obtain a terminallymodified acrylic polymer (conversion rate 96%).

Further, the obtained terminally modified acrylic polymer was measuredby NMR, and consequently, it could be verified that the acrylic polymerhad a functional group represented by the formula (2) at the end.

The obtained terminally modified acrylic polymer was analyzed by gelpermeation chromatography (GPC) using LF-804 Column manufactured bySHOKO Co., Ltd. as a column to determine a number average molecularweight on the polymethyl methacrylate equivalent basis and a molecularweight distribution (PDI=Mw/Mn). The results are shown in Table 1.

EXAMPLE 4 (Production of Acrylic Polymer)

A mixture solution of 30 mol of isobutyl methacrylate (manufactured byWako Pure Chemical Industries, Ltd.) as a monomer was added to 0.05 molof an organic bismuth compound CH₃C(CH₃)(Bi(CH₃)₂)COOCH₃ as a livingradical polymerization initiator, and then, the resulting mixture washeated to 100° C. while stirring the mixture with a stirrer andmaintained at this temperature for 3 hours. After the completion of areaction, the reaction solution was dissolved in 15 mL ofα,α,α-trifluorotoluene. To the resulting solution, 0.2 g of2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO manufactured by AldrichChemical Co.) was further added and the resulting mixture was reacted at80° C. for 1 hour. After the completion of a reaction, the resultingsolution was charged into 250 mL of hexane (manufactured by Wako PureChemical Industries, Ltd.) being stirred. Thereafter, a precipitatedpolymer was filtered under suction and dried to obtain a terminallymodified acrylic polymer (conversion rate 97%).

Further, the obtained terminally modified acrylic polymer was measuredby NMR, and consequently, it could be verified that the acrylic polymerhad a functional group represented by the formula (2) at the end.

The obtained terminally modified acrylic polymer was analyzed by gelpermeation chromatography (GPC) using LF-804 Column manufactured bySHOKO Co., Ltd. as a column to determine a number average molecularweight on the polymethyl methacrylate equivalent basis and a molecularweight distribution (PDI=Mw/Mn). The results are shown in Table 1.

EXAMPLE 5 (Production of Acrylic Polymer)

A mixture solution of 30 mol of isobutyl methacrylate (manufactured byWako Pure Chemical Industries, Ltd.) as a monomer was added to 0.001 molof an organic bismuth compound CH₃C(CH₃)(Bi(CH₃)₂)COOCH₃ as a livingradical polymerization initiator, and then, the resulting mixture washeated to 100° C. while stirring the mixture with a stirrer andmaintained at this temperature for 3 hours. After the completion of areaction, the reaction solution was dissolved in 15 mL ofα,α,α-trifluorotoluene. To the resulting solution, 0.2 g of2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO manufactured by AldrichChemical Co.) was further added and the resulting mixture was reacted at80° C. for 1 hour. After the completion of a reaction, the resultingsolution was charged into 250 mL of hexane (manufactured by Wako PureChemical Industries, Ltd.) being stirred. Thereafter, a precipitatedpolymer was filtered under suction and dried to obtain a terminallymodified acrylic polymer (conversion rate 93%).

Further, the obtained terminally modified acrylic polymer was measuredby NMR, and consequently, it could be verified that the acrylic polymerhad a functional group represented by the formula (2) at the end.

The obtained terminally modified acrylic polymer was analyzed by gelpermeation chromatography (GPC) using LF-804 Column manufactured bySHOKO Co., Ltd. as a column to determine a number average molecularweight on the polymethyl methacrylate equivalent basis and a molecularweight distribution (PDI=Mw/Mn). The results are shown in Table 1.

COMPARATIVE EXAMPLE 1 (Production of Acrylic Polymer)

30 mol of methyl methacrylate (manufactured by Wako Pure ChemicalIndustries, Ltd.) as a monomer was added to 1 mol of an organic bismuthcompound CH₃C(CH₃)(Bi(CH₃)₂)COOCH₃ as a living radical polymerizationinitiator, and then, the resulting mixture was heated to 100° C. whilestirring the mixture with a stirrer and maintained at this temperaturefor 3 hours. After the completion of a reaction, the reaction solutionwas dissolved in 15 mL of α,α,α-trifluorotoluene. To the resultingsolution, 1.2 mol of tributyltin hydride and 0.1 mol of AIBN were addedand the resulting mixture was reacted at 80° C. for 1 hour. After thecompletion of a reaction, the resulting solution was charged into 250 mLof hexane (manufactured by Wako Pure Chemical Industries, Ltd.) beingstirred. Thereafter, a precipitated polymer was filtered under suctionand dried to obtain an acrylic polymer with terminal hydrogen-modified(conversion rate 97%).

The obtained polymer was analyzed by gel permeation chromatography (GPC)using LF-804 Column manufactured by SHOKO Co., Ltd. as a column todetermine a number average molecular weight on the polymethylmethacrylate equivalent basis and a molecular weight distribution(PDI=Mw/Mn). The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 (Production of Acrylic Polymer)

30 mol of methyl methacrylate (manufactured by Wako Pure ChemicalIndustries, Ltd.) as a monomer was added to 1 mol of an organic bismuthcompound CH₃C(CH₃)(Bi(CH₃)₂)COOCH₃ as a living radical polymerizationinitiator, and then, the resulting mixture was heated to 100° C. whilestirring the mixture with a stirrer and maintained at this temperaturefor 3 hours. After the completion of the reaction, the reaction solutionwas dissolved in 15 mL of α,α,α-trifluorotoluene. To the resultingsolution, 1.2 mol of tributyltin deuteride and 0.1 mol of AIBN wereadded and the resulting mixture was reacted at 80° C. for 1 hour. Afterthe completion of a reaction, the resulting solution was charged into250 mL of hexane (manufactured by Wako Pure Chemical Industries, Ltd.)being stirred. Thereafter, a precipitated polymer was filtered undersuction and dried to obtain an acrylic polymer with terminaldeuterium-modified (conversion rate 97%).

The obtained polymer was analyzed by gel permeation chromatography (GPC)using LF-804 Column manufactured by SHOKO Co., Ltd. as a column todetermine a number average molecular weight on the polymethylmethacrylate equivalent basis and a molecular weight distribution(PDI=Mw/Mn). The results are shown in Table 1.

COMPARATIVE EXAMPLE 3 (Production of Acrylic Polymer)

30 mol of methyl methacrylate (manufactured by Wako Pure ChemicalIndustries, Ltd.) as a monomer was added to 1 mol of an organic bismuthcompound CH₃C(CH₃)(Bi(CH₃)₂)CN as a living radical polymerizationinitiator, and then, the resulting mixture was heated to 100° C. whilestirring the mixture with a stirrer and maintained at this temperaturefor 3 hours. After the completion of the reaction, the reaction solutionwas dissolved in 15 mL of α,α,α-trifluorotoluene. To the resultingsolution, 1.2 mol of tributyltin deuteride and 0.1 mol of AIBN wereadded and the resulting mixture was reacted at 80° C. for 1 hour. Afterthe completion of a reaction, the resulting solution was charged into250 mL of hexane (manufactured by Wako Pure Chemical Industries, Ltd.)being stirred. Thereafter, a precipitated polymer was filtered undersuction and dried to obtain an acrylic polymer in which an α end is2-cyanopropyl-2-yl and an ω end is deuterium-modified (conversion rate97%).

The obtained polymer was analyzed by gel permeation chromatography (GPC)using LF-804 Column manufactured by SHOKO Co., Ltd. as a column todetermine a number average molecular weight on the polymethylmethacrylate equivalent basis and a molecular weight distribution(PDI=Mw/Mn). The results are shown in Table 1.

COMPARATIVE EXAMPLE 4 (Production of Acrylic Polymer)

In a 1 liter three neck flask equipped with a reflux tube, 50 g ofmethyl methacrylate as a monomer and 350 g of toluene as a solvent weremixed and stirred, and the resulting mixture was heated to a temperatureat which a reflux was initiated. After the reflux, a solution formed bydissolving 10 g of AIBN (azobisisobutyronitrile) in 20 g of toluene wasadded to initiate polymerization. A temperature of the resulting mixturewas cooled to room temperature after a lapse of three hours from thestart of polymerization and thereby an acrylic polymer, in which apolymerization end is unknown, was prepared by a free radicalpolymerization method.

The obtained polymer was analyzed by gel permeation chromatography (GPC)using LF-804 Column manufactured by SHOKO Co., Ltd. as a column todetermine a number average molecular weight on the polymethylmethacrylate equivalent basis and a molecular weight distribution(PDI=Mw/Mn). The results are shown in Table 1.

<Evaluation>

The acrylic polymers obtained in Examples 1 to 5 and ComparativeExamples 1 to 4 were evaluated by the following method.

(Evaluation of Decomposition Properties (TG-DTA Evaluation))

Using a thermal decomposing apparatus (“simultaneous SDT 2960”manufactured by TA Instruments Co., Ltd.), the acrylic polymers obtainedin Examples 1 to 5 and Comparative Examples 1 to 4 were heated to 500°C. at a temperature rising rate of 10° C./min in an air atmosphere, anda temperature at which 50% by weight of the initial weight of theacrylic polymer is decomposed, and a ratio of the acrylic polymerremaining when the temperature of the acrylic polymer reaches 300° C.were measured, and the results are shown in Table 1.

Further, thermal decomposition behaviors at this time of Example 1 andComparative Examples 1 to 4 are shown in FIG. 1.

TABLE 1 Evaluation Ratio of acrylic Molecular Temperature at whichpolymer Conversion Number average weight 50% by weight of remaining whenrate molecular weight distribution the acrylic polymer reaching 300° C.(%) (Mn) (PDI) is decomposed (° C.) (%) Example 1 97 2900 1.12 290 41Example 2 95 3400 1.14 260 85 Example 3 96 3200 1.13 280 71 Example 4 9752400 1.12 280 41 Example 5 93 349000 1.12 290 45 Comparative 97 39001.08 345 86 Example 1 Comparative 97 4000 1.09 350 87 Example 2Comparative 97 4100 1.96 370 89 Example 3 Comparative — 11200 1.12 32064 Example 4

As shown in FIG. 1, in the terminally modified acrylic polymer obtainedin Example 1, a temperature at which most of the resin was decomposedwas lower than those of the terminally modified acrylic polymersobtained in Comparative Examples and particularly a thermaldecomposition property at a temperature of about 300° C. was extremelyhigh. On the other hand, the acrylic polymers obtained in ComparativeExamples 1 to 4 had poor thermal decomposition properties and most ofthe resins were not decomposed at a temperature of about 300° C.

EXAMPLE 6 (Production of Inorganic Fine Particle Dispersed PasteComposition)

5 g of the terminally modified acrylic polymer obtained in Example 1 wasdissolved in 10 g of toluene (manufactured by Wako Pure ChemicalIndustries, Ltd., boiling point 110° C.). To the resulting solution, 80g of silver powder (manufactured by MITSUI MINING & SMELTING Co., Ltd.,average particle diameter 2 μm) was added, and then, the resultingmixture was mixed and stirred until it becomes homogeneous by aplanetary mixing and defoaming machine to obtain a silver paste.

(Evaluation of Sintering Property)

The obtained silver paste was applied onto a glass plate so as to be 10μm in thickness with an applicator. The resulting applied substance wasdried at 120° C. for 10 minutes in an oven to remove a solvent, and theterminally modified acrylic polymer was decomposed and burnt at 450° C.for 10 minutes in a muffle furnace. Thereafter, silver was recovered andcarbon residue was measured by a total carbon/total sulfur measuringapparatus to yield a carbon content of 32 ppm (result is shown in Table2).

EXAMPLE 7 (Production of Inorganic Fine Particle Dispersed PasteComposition)

5 g of the terminally modified acrylic polymer obtained in Example 1 wasdissolved in 10 g of terpineol (manufactured by YASUHARA CHEMICAL Co.,Ltd., boiling point 215° C.). To the resulting solution, 80 g of silverpowder (manufactured by MITSUI MINING & SMELTING Co., Ltd., averageparticle diameter 2 μm) was added, and then, the resulting mixture wasmixed and stirred until it becomes homogeneous by a planetary mixing anddefoaming machine to obtain a silver paste.

(Evaluation of Sintering Property)

The obtained silver paste was applied onto a glass plate so as to be 10μm in thickness with an applicator. The resulting applied substance wasdried at 120° C. for 10 minutes in an oven to remove a solvent, and theterminally modified acrylic polymer was decomposed and burnt at 450° C.for 10 minutes in a muffle furnace. Thereafter, silver was recovered andcarbon residue was measured by a total carbon/total sulfur measuringapparatus to yield a carbon content of 41 ppm (result is shown in Table2).

EXAMPLE 8 (Production of Inorganic Fine Particle Dispersed PasteComposition)

5 g of the terminally modified acrylic polymer obtained in Example 1 wasdissolved in 10 g of toluene (manufactured by Wako Pure ChemicalIndustries, Ltd., boiling point 110° C.). To the resulting solution, 80g of silver powder (manufactured by MITSUI MINING & SMELTING Co., Ltd.,average particle diameter 2 μm) was added, and then, the resultingmixture was mixed and stirred until it becomes homogeneous by aplanetary mixing and defoaming machine to obtain a silver paste.

(Evaluation of Sintering Property)

The obtained silver paste was applied onto a glass plate so as to be 10μm in thickness with an applicator. The resulting applied substance wasdried at 120° C. for 10 minutes in an oven to remove a solvent, and theterminally modified acrylic polymer was decomposed and burnt at 300° C.for 30 minutes in a muffle furnace. Thereafter, silver was recovered andcarbon residue was measured by a total carbon/total sulfur measuringapparatus to yield a carbon content of 68 ppm (result is shown in Table2).

EXAMPLE 9 (Production of Inorganic Fine Particle Dispersed PasteComposition)

5 g of the terminally modified acrylic polymer obtained in Example 2 wasdissolved in 10 g of terpineol (manufactured by YASUHARA CHEMICAL Co.,Ltd., boiling point 215° C.). To the resulting solution, 20 g ofphosphor powder (manufactured by NICHIA Corp., particle diameter 3 μm)was added, and then, the resulting mixture was mixed and stirred untilit becomes homogeneous by a planetary mixing and defoaming machine toobtain a phosphor paste.

(Evaluation of Sintering Property)

The obtained phosphor paste was applied onto a glass plate so as to be10 μm in thickness with an applicator. The resulting applied substancewas dried at 120° C. for 10 minutes in an oven to remove a solvent, andthe terminally modified acrylic polymer was decomposed and burnt at 300°C. for 30 minutes in a muffle furnace. Thereafter, the phosphor powderwas recovered and carbon residue was measured by a total carbon/totalsulfur measuring apparatus to yield a carbon content of 56 ppm (resultis shown in Table 2).

EXAMPLE 10 (Production of Inorganic Fine Particle Dispersed PasteComposition)

5 g of the terminally modified acrylic polymer obtained in Example 4 wasdissolved in 10 g of terpineol (manufactured by YASUHARA CHEMICAL Co.,Ltd., boiling point 215° C.). To the resulting solution, 20 g of greenphosphor powder (manufactured by NICHIA Corp., particle diameter 3 μm)was added, and then, the resulting mixture was mixed and stirred untilit becomes homogeneous by a planetary mixing and defoaming machine toobtain a phosphor paste.

(Evaluation of Sintering Property)

The obtained phosphor paste was printed on a glass plate by using aprinting screen with a pattern of line and space of 50 μm/100 μm inwidth and 5 cm in length and a screen printing machine. As the resultsof printing, a line pattern of line and space of 63 μm/88 μm in widthwas achieved. The resulting printed matter was dried at 120° C. for 10minutes in an oven to remove a solvent, and the terminally modifiedacrylic polymer was decomposed and burnt at 300° C. for 30 minutes in amuffle furnace. Thereafter, the green phosphor powder was recovered andcarbon residue was measured by a total carbon/total sulfur measuringapparatus to yield a carbon content of 68 ppm (result is shown in Table2).

EXAMPLE 11 (Production of Inorganic Fine Particle Dispersed PasteComposition)

5 g of the terminally modified acrylic polymer obtained in Example 4 wasdissolved in 10 g of terpineol (manufactured by YASUHARA CHEMICAL Co.,Ltd., boiling point 215° C.). To the resulting solution, 20 g of glassfrits (“ABX 169F” manufactured by Tokan Material Technology Co., Ltd.,melting point 464° C., particle diameter 2.5 μm) was added, and then,the resulting mixture was mixed and stirred until it becomes homogeneousby a planetary mixing and defoaming machine to obtain a glass paste.

(Evaluation of Sintering Property)

The obtained glass paste was applied onto a glass plate so as to be 10μm in thickness with an applicator. The resulting applied substance wasdried at 120° C. for 10 minutes in an oven to remove a solvent, and theterminally modified acrylic polymer was decomposed and burnt at 300° C.for 30 minutes in a muffle furnace. Thereafter, the glass frits wererecovered and carbon residue was measured by a total carbon/total sulfurmeasuring apparatus to yield a carbon content of 71 ppm (result is shownin Table 2).

EXAMPLE 12 (Production of Inorganic Fine Particle Dispersed PasteComposition)

A metal oxide paste was obtained in the same manner as in Example 11except for using 20 g of ITO powder (manufactured by Aldrich ChemicalCo., average particle diameter 0.03 μm) in place of 20 g of glass frits.

(Evaluation of Sintering Property)

The obtained metal oxide paste was applied onto a glass plate so as tobe 10 μm in thickness with an applicator. The resulting appliedsubstance was dried at 120° C. for 10 minutes in an oven to remove asolvent, and the terminally modified acrylic polymer was decomposed andburnt at 300° C. for 30 minutes in a muffle furnace. Thereafter, ITO wasrecovered and carbon residue was measured by a total carbon/total sulfurmeasuring apparatus to yield a carbon content of 59 ppm (result is shownin Table 2).

EXAMPLE 13 (Production of Inorganic Fine Particle Dispersed PasteComposition)

A metal oxide paste was obtained in the same manner as in Example 11except for using 20 g of ZnO powder (manufactured by Aldrich ChemicalCo., average particle diameter 1 μm) in place of 20 g of glass frits.

(Evaluation of Sintering Property)

The obtained metal oxide paste was applied onto a glass plate so as tobe 10 μm in thickness with an applicator. The resulting appliedsubstance was dried at 120° C. for 10 minutes in an oven to remove asolvent, and the terminally modified acrylic polymer was decomposed andburnt at 300° C. for 30 minutes in a muffle furnace. Thereafter, ZnO wasrecovered and carbon residue was measured by a total carbon/total sulfurmeasuring apparatus to yield a carbon content of 67 ppm (result is shownin Table 2).

COMPARATIVE EXAMPLE 5 (Production of Inorganic Fine Particle DispersedPaste Composition)

5 g of the acrylic polymer obtained in Comparative Example 1 wasdissolved in 10 g of toluene (manufactured by Wako Pure ChemicalIndustries, Ltd., boiling point 110° C.). To the resulting solution, 80g of silver powder (manufactured by MITSUI MINING & SMELTING Co., Ltd.,average particle diameter 2 μm) was added, and then, the resultingmixture was mixed and stirred until it becomes homogeneous by aplanetary mixing and defoaming machine to obtain a silver paste.

(Evaluation of Sintering Property)

The obtained silver paste was applied onto a glass plate so as to be 10μm in thickness with an applicator. The resulting applied substance wasdried at 120° C. for 10 minutes in an oven to remove a solvent, and theacrylic polymer was decomposed and burnt at 300° C. for 30 minutes in amuffle furnace. Thereafter, silver was recovered and carbon residue wasmeasured by a total carbon/total sulfur measuring apparatus to yield acarbon content of 1400 ppm (result is shown in Table 2).

TABLE 2 Carbon residue (ppm) Example 6 32 Example 7 41 Example 8 68Example 9 56 Example 10 68 Example 11 71 Example 12 59 Example 13 67Comparative 1400 Example 5

INDUSTRIAL APPLICABILITY

In accordance with the present invention, it is possible to provide aterminally modified acrylic polymer having excellent thermaldecomposition properties at low temperatures, an inorganic fine particledispersed paste composition obtained by using the terminally modifiedacrylic polymer and a method of producing of the terminally modifiedacrylic polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of thermal decomposition behavior on acrylic polymersobtained in Example 1 and Comparative Examples 1 to 4 measured by usinga thermal decomposing apparatus.

FIG. 2 is an NMR spectrum of the terminally modified acrylic polymerobtained in Example 1.

1. A terminally modified acrylic polymer, which comprises a main chaincomposed of a repeating unit represented by the following formula (1),and a group represented by the following formula (2) at both ends or oneend of the main chain,

wherein R¹ represents hydrogen atom, an organic group having 1 or morecarbon atoms or a derivative of an organic group having 1 or more carbonatoms; R² represents an organic group having 1 or more carbon atoms or aderivative of an organic group having 1 or more carbon atoms; R³ and R⁴each represents hydrogen atom, an organic group having 1 or more carbonatoms or a derivative of an organic group having 1 or more carbon atoms;and n represents a positive integer.
 2. The terminally modified acrylicpolymer according to claim 1, which comprises a segment derived from amethacrylic ester.
 3. The terminally modified acrylic polymer accordingto claim 1, wherein R² is an alkyl group having 1 to 8 carbon atoms. 4.The terminally modified acrylic polymer according to claim 1, wherein R³and R⁴ each is hydrogen atom.
 5. The terminally modified acrylic polymeraccording to claim 1, wherein the number average molecular weight is2000 to
 500000. 6. An inorganic fine particle dispersed pastecomposition, which comprises the terminally modified acrylic polymeraccording to claim 1, an organic solvent, and an inorganic fineparticle.
 7. The inorganic fine particle dispersed paste compositionaccording to claim 6, wherein a boiling point of the organic solvent is100 to 290° C. at 1 atm.
 8. The inorganic fine particle dispersed pastecomposition according to claim 6, wherein the inorganic fine particle isa glass frit, a phosphor powder, a silver powder, a copper powder, anITO powder, a zinc oxide powder or a carbon powder.
 9. A method ofproducing a terminally modified acrylic polymer, comprising a step ofreacting a living radical polymerization initiator represented by theformula (3-1) or (3-2) with an acrylic monomer represented by theformula (4) to prepare an acrylic polymer, and a step of reacting saidacrylic polymer with a nitroxyl radical represented by the formula (5)or (6) to modify both ends or one end of said acrylic polymer,

wherein R⁵ to R¹² each represents hydrogen atom, an organic group having1 or more carbon atoms or a derivative of an organic group having 1 ormore carbon atoms, R¹³ represents a derivative of a divalent organicgroup having 3 or more carbon atoms, and X represents Bi, Te, Sb oriodine, provided that X is not replaced with R⁶ when X is iodine.